A baseline configuration for the dual-aircraft platform (DAP) concept is described and evaluated in a physics-based flight dynamics simulations for two month-long missions as a communications relay in the lower stratosphere above central Florida. The DAP features two unmanned aerial vehicles connected via a long adjustable cable which effectively sail back-and-forth using wind velocity gradients and solar energy. Detailed atmospheric profiles in the vicinity of 60,000-ft derived from archived data measured by the 50-Mhz Doppler Radar Wind Profiler at Cape Canaveral are used in the flight simulations. An overview of the novel guidance and flight control strategies are provided. The energy-usage of the baseline configuration during month-long stationkeeping missions (i.e., within 150-mile radius of downtown Orlando) is characterized and compared to that of a pure solar aircraft.
I. Introduction
A. BackgroundAircraft platforms which could stationkeep in the stratosphere for years, referred to as atmospheric satellites, represent a long-standing, grand challenge to the aeronautics community, and have enormous potential societal and economic impact. Such platforms would diversify and expand surveillance capabilities (e.g., NASA's earth science missions) and communications bandwidth and availability (e.g., for underserved remote areas of the US, emergency communications), at a fraction of the cost of orbital satellite networks. Constellations of such platforms might potentially be integrated into the National Airspace System (NAS) to facilitate inter-aircraft communications or to support navigation or for aircraft surveillance. Constellations of such platforms could also improve communications and surveillance capabilities along major shipping lanes.NASA and DARPA, and more recently industry, has funded development of aircraft which rely on solely solar power for propulsion, and the vehicles must accumulate and store a substantial amount of power during the day to operate at night. This is further compounded by the large variability of available solar energy during the year and the inability to point aircraft wings towards the sun to improve solar power capture. These factors result in severe limitations on the power that can be made available to the payload for communications, surveillance, etc.
B. Dual-Aircraft PlatformThe Dual-Aircraft Platform (DAP), illustrated in Figure 1, is a concept for achieving a low-cost atmospheric satellite [1,2] which utilizes wind shear as the primary energy source, and has the potential to stationkeep for very long periods of time, providing substantial levels of power for its payload. DAP consists of two glider-like Unmanned Aerial Vehicles (UAVs) connected via a thin, strong cable which literally sails without propulsion, using levels of wind shear commonly found in lower Stratosphere (e.g., near 60,000-ft). The two aircraft are positioned at different altitudes, as far as 2,000-ft apart, to encounter substantially different wind velocities. The device operates similar in principle t...